Effects of AC interference on the optimum cathodic protection potential of X70 steel in soil solution

Abstract

PurposeThe presence of alternating current (AC) causes serious damage on buried pipelines, even when the off potential meets the −0.85 V/CSE criterion. The optimum cathodic protection potential (OCPP) is more reliable for cathodic protection. The purpose of this paper is to study the effects of AC on the OCPP and, using electrochemical impedance spectroscopy (EIS), to investigate how to get the optimum cathodic protection.Design/methodology/approachThe paper describes the application of EIS to investigate the OCPP of X70 steel in a soil simulating solution with different AC interferences.FindingsThe experimental results indicate that AC interference makes the OCPP decrease. It was determined that the −0.85 V/CSE criterion is not appropriate when there is AC interference. When the AC voltage was less than 6 V, the OCPP was approximately −900 mV/SCE, whereas when the AC voltage was more than 7 V, the OCPP was approximately −1,000 mV/SCE.Originality/valueAlthough there have been previous research studies on the OCPP, this paper is the first to study the effects of AC interference on the OCPP and it has been confirmed that the OCPP changed when AC interference is present.